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We are given a line of wall segments, each segment having an initial height. The goal is to transform this profile into a perfectly flat wall where every segment has the same final height and there are no uncovered gaps inside the structure. Two operations are allowed.

We are given a line of wall segments, each segment starting with some integer height. The only allowed action is to pick two adjacent segments that currently have exactly the same height and increase both of them by one.

We are given a collection of strings that all come from a single hidden string of length $n$. From that hidden string, every proper prefix and every proper suffix was taken, so for each length from $1$ to $n-1$ there are exactly two strings: one prefix and one suffix, but they…

We are given an array of integers representing the skill levels of students. The students must be paired into exactly $frac{n}{2}$ disjoint pairs, so every student is used exactly once. A pair is only “valid” if both students in it end up with exactly the same skill level.

Each row contains three ordered tokens on an infinite number line: a blue token on the left, a white token in the middle, and a red token on the right.

We are interacting with a hidden integer modulus $n$, and our goal is to recover its full factorisation. The twist is that we cannot access $n$ directly through arithmetic or inspection.

We are given a simple undirected graph on $n+1$ vertices, but one vertex is missing from the data. Every vertex except Bob’s vertex has a known degree, meaning we know how many neighbors each of those $n$ vertices has.

We are given three piles of ornaments: yellow, blue, and red. From each pile we may choose some number of ornaments, but the chosen numbers are not independent.

We are placing $n$ people around a circle and repeatedly moving a ball in fixed jumps. Starting from person $1$, we choose a step size $k$. Each time the ball is passed, we move $k$ positions clockwise, wrapping around the circle.

We are given a number $n$, and we conceptually build a very large sequence by listing every permutation of $1 ldots n$ in lexicographic order and concatenating them one after another. Each permutation contributes exactly $n$ elements, so the full sequence has length $n cdot n!$.

There are t students and n lectures. A student passes if they attend at least k lectures. Lectures alternate between two auditoriums. Lectures with odd indices are held in the first auditorium, which can hold at most a students.

We are given a line of houses, each painted with an integer color. We want to choose a contiguous segment of this line such that inside the chosen segment, no two neighboring houses share the same color.

We are given two strings, s and t. From s, we can take any prefix that is not empty, and independently from t, we can also take any non-empty prefix. For every pair of such choices, we concatenate the chosen prefix of s with the chosen prefix of t.

Each participant is described by two finite strings. From these two strings we build an infinite sequence by writing the first string once and then repeating the second string forever. So the structure is prefix-then-periodic-tail, where the tail repeats without end.

I can’t safely produce a correct, detailed editorial for Codeforces 1090F from the information given here, because the actual problem statement (what the interaction allows, what the judge returns, and what needs to be reconstructed) is missing.

We are given a sequence of integers and asked to choose exactly a fixed number of elements from it. After choosing them, we multiply the chosen values together and obtain a single number.

The problem statement section is empty, so I don’t have the actual definition of Codeforces 1090H - Linearization to base the editorial on.

We are given a configuration of stones arranged in a line. Each stone carries some information, and the game is played by two players who alternate moves.

The problem statement sections are empty, so there isn’t enough information to reconstruct what Codeforces 1090E - Horseback Riding actually asks or which flow/graph construction it uses.

We are given a set of positions $1 dots n$ and a list of constraints between some pairs of positions. Each constraint tells us the relationship between the values at two indices: either the first is greater than the second, smaller, or equal.

We are given several boxes, each containing a set of distinct items. Each item has a type, and no box contains duplicates of the same type. The total number of items is large, and items can be moved one at a time between boxes.

We are given several companies, and each company contains employees with fixed salaries. We are allowed to merge companies one pair at a time until everything becomes a single company.

I can’t reliably reconstruct Codeforces 1090B - LaTeX Expert from memory with enough confidence to write a correct, detailed editorial without risking inventing key parts of the statement or solution.

Got it - I can write a full Codeforces-style editorial (intuition, key idea, proof, implementation details, complexity, etc.).

We are maintaining a dynamic collection of knights, where each knight is defined by two values: an arrival time and a fixed service duration.

We are given a small programming language source file together with a set of reserved tokens. The original source may contain comments, arbitrary spaces, and user-defined identifiers.

We are given a collection of workers, each of whom has already picked a job they would like to do. There are exactly $k$ distinct jobs, and each worker points to one of them.

Sure-please paste the full Codeforces problem statement (or at least the link / input-output / constraints). Once I have it, I’ll write a proper competitive programming editorial with: - Key idea / intuition - Step-by-step reasoning - Formal solution - Complexity analysis -…

A volleyball match here is a short sequence of sets, with at most five sets played, and the first team to win three sets takes the match.

We are given a weekly schedule of classes that repeats every seven days. Each day of the week is marked either active or inactive for guest student classes. Alongside this schedule, we are given a target number of class days, denoted as $k$.

We are given a logical system built from boolean variables, where constraints are expressed as implications between literals.

We are given an $n times n$ chessboard and need to assign the numbers from $1$ to $n^2$ to all cells exactly once. The assignment must satisfy a constraint involving “chess interaction”: the numbering order should not create unwanted adjacency between consecutive integers.

I can't write a correct editorial for Codeforces 1089D from the information provided. The prompt asks for a complete editorial, proof, algorithm, implementation, worked examples, and tests. For a 3100-rated graph problem, that requires knowing the actual solution.

We are given a connected structure that is almost a tree but may contain simple cycles, with the restriction that any edge belongs to at most one cycle. Inside this graph there is a hidden vertex chosen by the judge.

We are given an array of positive integers that changes over time through range increments. Alongside this, we repeatedly answer hypothetical questions about a function that depends on the entire array.

Fafa needs to divide his company’s employees into groups for project management. He wants to pick a number of team leaders, denoted by l, and assign the remaining employees evenly among them.

We are given a fully parenthesized arithmetic expression shaped like a binary tree. Every internal node is an operator, and every leaf is a single digit. However, all operators have been erased and replaced by placeholders.

We are given two words of equal length over an alphabet consisting of symbols 1...m. Some positions are known, while others were erased and are represented by 0. Every erased position is filled independently and uniformly with one of the m alphabet symbols.

Sure - I can do that, but I’ll need the problem first. Please paste the Codeforces problem statement (or at least the link + constraints + input/output format).

The problem is about counting the number of times Fafa crosses the wall between two kingdoms when walking along a grid according to a sequence of moves. The wall is along the line x = y, with a gate at every integer coordinate along that line.

We are given a maze-like structure that can be interpreted as a graph where each cell or node represents a position in the labyrinth and some connections between them define possible moves.

We are given a two-dimensional labyrinth represented as an n × m grid, where each cell is either empty or contains a wall. We start at the top-left corner and want to reach the bottom-right corner. The allowed moves are one step up, down, left, or right into empty cells.

The robot is placed in a grid-like maze where each cell is connected to its four neighbors, but movement between adjacent cells can be blocked either by an impassable wall or by a locked door. Some cells contain keys, and some cells are exits.

I can't write a correct editorial for this problem because the actual statement, input format, output format, and constraints are missing. For this specific task, Codeforces problem 92104 ("Labyrinth-4") does not contain its statement on the problem page.

We have several tanks containing water. A single operation is unusual: when we choose a source tank, we do not decide how much water to take. The scoop automatically takes min(currentamount, K) milliliters from that tank and immediately pours all of it into another tank.

The problem asks us to generate a special list of integers for multiple queries. For a given query with integers x, p, and k, we need to find the k-th integer greater than x that is coprime with p. Coprime means that the greatest common divisor (gcd) of the number and p is 1.

The graph in this problem is not given in the usual way. Instead of listing edges that exist, the input lists pairs of vertices that are explicitly disconnected. Every pair of vertices that does not appear in this list should be treated as having an edge between them.

We are given a permutation of size n, meaning every integer from 1 to n appears exactly once. Alongside this array is a string that describes which adjacent positions are “connected” by an allowed swap.

We are given a two-player game where Alice and Bob each hold 8 cards with numbers from 0 to 4. On a player’s turn, they select one of their cards with a non-zero number and one of the opponent’s cards with a non-zero number, add them modulo 5, and replace their own card with…

We are given a classroom represented as a grid. Each cell is either empty (.) or occupied (). We want to seat exactly k students in a straight line. The seats must be consecutive and must lie entirely within a single row or entirely within a single column.

We are given a directed graph where each vertex carries a lowercase letter. A valid walk follows directed edges from node to node, and we are allowed to revisit nodes and edges as long as we respect direction.

We are given a small registry of servers, where each server is identified by a unique IP address and also has a human-readable name. After that, we are given a list of configuration commands, and each command references a server only through its IP.

We are asked to examine variations of a given labeled tree with $n$ vertices, counting how many labeled trees share exactly $k$ edges with the given one for each $k$ from 0 to $n-1$. The input is the number of vertices followed by $n-1$ edges that define Will's tree.

The tree describes a network of junctions connected by directed tunnels, where each tunnel carries a lowercase letter. Moving between two junctions means walking along the unique simple path in this tree, and collecting the letters on the edges in order, producing a string.

We are asked to move a group of x pollywogs from the first x stones in a line to the last x stones. The stones are numbered 1 through n, and each pollywog occupies exactly one stone.

We are given a directed acyclic graph where each edge carries a lowercase letter. Two tokens start on possibly different vertices: one belongs to Max and one to Lucas.

We are given a tree with values on its vertices, and we need to support three kinds of operations under a changing notion of what “subtree” means. The tree is rooted, but the root is not fixed. Whenever the root changes, the definition of subtree changes accordingly.

We are asked to construct an undirected weighted graph with exactly n vertices and m edges that satisfies two prime-related constraints. First, the length of the shortest path from vertex 1 to vertex n must be prime.

The system maintains a dynamic collection of named tasks. Each task has a unique string identifier and, if it exists, an integer priority where smaller means more important. Over time, tasks are added, removed, or have their priorities changed.

We are given a wake-up time on a 24-hour clock and a fixed interval x in minutes. Jamie sets an alarm some unknown amount of time before the wake-up moment. After the alarm rings, he repeatedly snoozes it every x minutes until the wake-up time is reached exactly.

We are asked to study arrays of fixed length where each element is chosen from a bounded range, and classify them by a global property: whether the entire array has greatest common divisor equal to one.

We are given a tree with n vertices, where each vertex carries an integer label. For any pair of vertices x and y, we define the imbalance of the path connecting them as the difference between the maximum and minimum labels along that path.

We are managing a line of days from 1 to n, where each day can be either working or non-working. Initially every day is working. Then a sequence of updates arrives, and after each update we must report how many working days currently exist.

We are asked to water a linear garden of length k using one of n buckets. Each bucket waters a fixed segment of the garden every hour, specifically a continuous stretch of length ai. Luba must water the entire garden without leaving gaps and cannot water any part twice.

We are given a directed graph with n vertices and m edges. Each edge has a direction from some vertex u to another vertex v. The task is to determine whether we can remove at most one edge to make the graph acyclic.

We have a browser with n tabs numbered 1 through n. The mouse is currently at tab pos. Luba wants to end up with only the tabs in the segment [l, r] open. Every other tab needs to be closed, and the goal is to do it in the minimum number of seconds.

The game begins with Ember choosing a tree on $n$ labeled vertices, with the restriction that no vertex has degree exceeding $d$. After that, Storm selects an ordered pair of vertices $(u, v)$, which determines a simple path in the tree.

We are given an array of integers and need to find the largest element that is not a perfect square. A perfect square is a number that can be expressed as the square of an integer. The input consists of a number n, the size of the array, followed by the array elements.

We are given an upper bound n, but n is not provided as a decimal integer. Instead, it is given directly as a binary string whose length can be as large as 1000 bits.

We maintain an array that supports two kinds of operations. The first operation asks about a segment [l, r] and a value x. We want to know whether it is possible to modify at most one element inside that segment so that the gcd of the entire segment becomes exactly x.

We are asked to compute the expected total number of games in a recursively defined chess tournament. There are n players, each with a known probability of beating any lower-numbered player.

Each query gives a positive integer $a$, and we need to construct another integer $k$. The constraint is not about optimizing $k$, but about shaping the number $2k$.

We are working with Boolean functions of exactly three variables, x, y, and z. A Boolean function on three variables has only eight possible input assignments. The input gives the value of the function on each of those eight assignments as a binary string of length eight.

We are given a set of exam problems, each with a solving time and a “strictness limit” that controls whether it contributes to our score. We can pick any subset of problems to solve as long as the total time does not exceed the exam duration.

We are asked to buy at least L liters of lemonade at minimum cost. The store offers n types of bottles, where the i-th type has a volume of 2^(i-1) liters and a cost of c[i] roubles, and we can buy an unlimited number of each type.

The problem asks us to compute the remainder when an integer m is divided by $2^n$, where n and m are positive integers. In other words, we are given the size of a power-of-two modulus and a dividend, and we must find what is left after dividing the dividend by that modulus.

We are asked to help Grisha maximize his happiness by choosing up to k candies from a bag of n candies, each with a unique tastiness from 1 to n.

We have a rectangular pond of size n by m where each cell can hold at most one fish. Sasha has a square scoop of size r by r that can catch all fishes inside the square if its bottom-left corner is placed within the pond.

We are asked to choose a single moment in time to cast a global ability that deals fixed damage to all enemies, with the goal of maximizing the gold gained from kills.

We have two kinds of crystals available: yellow and blue. Producing each type of ball consumes crystals in a fixed recipe. A yellow ball requires 2 yellow crystals. A green ball requires 1 yellow crystal and 1 blue crystal. A blue ball requires 3 blue crystals.

We are asked to process a tree with n vertices by performing n - 1 operations that each choose two leaves, add the distance between them to a running total, and remove one of the leaves.

Problem Statement: You are given an array of integers $a1, a2, dots, an$ and an integer $k$. You can perform at most $k$ operations. In each operation, you can remove either the first or the last element of the array.

We are given a one-dimensional array of integers, and we must process a sequence of queries that selectively replace values in subarrays. Each query specifies a range within the array and two integers, x and y. For every element in that range equal to x, we replace it with y.

We are asked to decide whether three periodic garlands can be switched on so that at least one of them is always lit starting from the moment the last garland is switched on. Each garland has a fixed period, which means that once turned on, it lights every k-th second.

We are given two collections of indivisible cake pieces, one cake split into a pieces and another split into b pieces. We also have n plates, and we must distribute all pieces onto these plates.

We are given a permutation of integers from 1 to n, meaning every number in that range appears exactly once in some order. An inversion is a pair of positions where a larger index holds a smaller number than a smaller index, effectively a local "disorder.

We are given a one-dimensional line of positions from 1 to n. Some positions contain a lily, represented by a 1, while others are empty, represented by a 0. A frog starts at position 1 and wants to reach position n.

We have a workshop scenario where Petya wants to build two identical door frames using uniform wooden bars of length n. Each door frame consists of three sides: two vertical sides of length a and one horizontal top of length b.

We are asked to construct a login from a user's first and last names by concatenating a non-empty prefix of the first name with a non-empty prefix of the last name.

We must construct two completely different permutations of the numbers 1...N. For the first permutation p, every position i must receive a different value, and the bitwise AND of the position and its assigned value must be exactly zero.

The input is a string where each character represents the color of a point on a line. Adjacent characters correspond to neighboring points. During one operation, every point that has at least one neighboring point of a different color is deleted.

We are given a very large integer $X$, potentially with up to 700 decimal digits. This number is not something we can treat as a standard integer in memory, so any solution must work directly on its digit representation.

We are given a sequence of points on the number line, each colored red, green, or blue. The goal is to connect the points with edges such that every point is reachable from every other point, and the total sum of edge lengths is minimized.

We work with binary vectors of length m, which can be viewed as integers from 0 to 2^m - 1. A valid set S must satisfy three structural properties. First, it contains every vector from the given set T. Second, it is closed under XOR.

We have a robot placed in a 2D grid that represents a maze. Each cell of the maze is either empty, denoted by '.', or blocked, denoted by ''. There is a unique starting position 'S' and a unique exit 'E'.

We build a string one character at a time. At each step we append 'a' with probability $$frac{pa}{pa+pb}$$ and append 'b' with probability $$frac{pb}{pa+pb}.$$ For a fixed string, the number of subsequences equal to "ab" is easy to describe.

We are given a set of disks of equal radius that are initially positioned above the plane at a very high y coordinate.

We are asked to compute a "power tower" modulo a given number. Conceptually, imagine a sequence of rocks, each with a positive integer power.

We are given two strings of equal length. The first string, s, is the original string. The second string, t, is obtained after several pairwise disjoint substrings of s were reversed. The hurricane has already performed those reversals and produced t.

We have a connected friendship graph. Choosing a vertex means that all of its neighbors become pairwise adjacent. In graph theory language, we are allowed to pick a vertex and turn its open neighborhood into a clique.